Control system for aircraft turbosuperchargers



Aug. 12, 1947- M. A. EDWARDS ETAL 2,425,697 CONTROL SYSTE" FOR AIRCRAFT TURBOSUPERCHARGERS Filed June 5, 1945 Inventors: Martin A- Edwards, Hugh M- 9 b WW5 y 'T'hen'- Attorney.

Patented Aug.'12, 1947 UNITED STATES PATENT. OFF-[C CONTROL SYSTEM FOR AIRCRAFT I TURBOSUPERCHARGERS Martin A. Edwards, Scotia, and Hugh, M. Ogle, Schenectady, N. Y., as'signors to General Electric Company, a corporation of New York Application June 5, 1943, Serial No. 489,798

Our invention relates to a control system for aircraft turbosuperchargers and especially to control system for turbosuperchargers wherein the turbosupercharger is operated by exhaust gases from an aircraft internal combustion engine and the air compressed by the turbosupercharger is used to supercharge the engine.

It is an object of our invention to provide a new and improved control chargers for aircraft.

It is another object of our invention to provide system for turbosuper- 'new and improved regulating means for turbosuperchargers which maintain constant a predetermined pressure appurtenantto the operation of the supercharger such, for example, as compressor discharge or carburetor inlet pressure,

. and furthermore to maintain this pressure over a predetermined range of' operationwith great stability.

It is another object of 'our invention to provide new and improved means for regulating a turbosupercharger in which the only connections between those component parts of the regulating means which are widely separated are electrical and all 'long fluid and mechanical connections are dispensed with.

8-ClaimS. (Cl. 23011) indicated at ii. The tuiibine wheel of the charger i5 is indicated at it and the compressor at ll. Connected with the nomle box it is a waste gate conduit llin whichis located an adjustable waste gate or waste valve I! used in regulating the turbosupercharger. On the shaft of the waste gate I9 is fixed an arm or crank for use in positioning the gate or valve means is. Connected to the inlet ofcompressor l1 is'an intake conduit 2| for conveying air from the slip v stream of the aircraft to the compressor. To this end conduit 2| is connected with a suitable ram cm which faces into the slip stream of the air craft. The discharge side of compressor I1 is connected by a conduit 23 to the intake of car buretor i 2. If desired a suitable intercooler such as is indicated at 24 may be provided in conduit' 23 to maintain the temperature of the air enterpredetermined range ing carburetor l2 within a for best airplane performance.

The arrangement so far described is a known one and is to be taken as typical of any turbosupercharger installation.- In operation exhaust, gases from the air craft engine are supplied through exhaust manifold l I and a suitable conduit, if this is necessary, to the nomle box I 4-. from Still another object of our invention is to pro-- I reference may be had to the accompanying drawin in which Fig. 1 is a diagrammatic view of a turbosupercharger control system embodying ourinvention, and Fig. 2 is a curve diagram to aid in understanding our invention.

Referring now to the drawing, I 0 indicates an aircraft internal combustion engine having an intake manifold not shown and an exhaust manifold, only a portion of which is shown at II. A carburetor I2 is schematically indicated as having its outlet connected to the intake. manifold (not shown) as by means of a conduit I 3. Exhaust manifold l l is connected either directly or through a suitable conduit to the nozzle box ll of an exhaust gas-driven supercharger generally which they are discharged through a ring of noz-,.

zles to the turbine wheel 16 of supercharger."

' or through waste conduit I8 directly to atmosphere. When wastegate I9 is wide open sub-.

stantially all the exhaust gases discharge directly to atmosphere, little if any passing through the nozzles to the turbine wheel It. This represents no load on the supercharger. As waste gate I9 is gradually closed, pressure is built up in nwzle box It eflecting a gradually increasingflow of exhaust gases through the nozzles to the turbine wheel to operate the supercharger. The maximum load on the supercharger is reached when waste gate I9 is fully closed so that all gases from the engine are discharged against the turbine wheel l6. Ordinarily waste gate l 9 is in an intermediateposition, part'of the exhaust gases being discharged to atmosphere and the remainder passing through the turbine wheel I 6.

Our invention has to do particularlywith im- I proved means for-regulating waste gate l0, and consists essentially of six elements the connections between'which are solely electrical. These: elements comprise a control box generallyindicated at "25, a manual pressure-setting means 7 generally] indicated at 26, a pressure unit generally indicated at 21, an amplifier generally indigate drive unit generally cated at 28. a waste 29 and a tachometer generator l0.

I ammo? the cabin N. The pressure unit 2'I is mounted closely adjacent! the .point at which pressure corresponding to the pressure to be regulated vis obtained, while similarly the wasteegate drive unit 29 is mounted closely adjacent to :the waste vgate 1'9 :and also tachometer generator '30 driven fromsupercharger i5 is mounted closely adjacent .to turbosupercharger l5, thereby permitting that fluid, mechanicaLor connections other than .-elec-,

trical connections may be maintained-at absolute minimum.

Theposition of waste gateiSmay-bevaried by any suitablenneanssuch, for example, as a hy- -draullc-pistt1i or the .like. However, due to the very low temperatures encountered by high flying lair craft, the oil used to operate a pistonor similard'evice isilikely tocongeal and unsatis- ..'tactory operation :results. Preferably, therefore, we have .aillustratedthe waste gate drive .unit 29 movement of the arm or-crank occurs The mechanical connectionsbetween motor 32 and arm-20 comprise a shaft flpsuitable gearing 34,

.shaftfifl'. crank 35 .and .linkL36c Link .36 interconnects theends'oracranksin:sand35. The extreme positions of waste vgate is are .determined suitable sstop means '31 :38 respectively.

The operation 'ofxmotor '32 .andconsequently the position of waste'cgate .19 may :be controlled,

as willtbeiobviousiromitheiollowing description,

in responsetowany pressure appurtenant :tofan operating condition of :the supercharger I 5 such,

for example, as the compressor discharge or carburetor'inlet pressure. lt'ihas beeni'oun'd de- ,that as the :air craft .rises the speed v.o'tzthe supercharger :nmstincrease "to maintain :this pressure constant. When .a :;predetermined critical speed is reached, it is not .feasible to :permit further pressure is obtained. It .is-sdesirable to "control motor 32 which positions waste .gate is seas-to maintain constant a predetermined pressure appurtenant tosan operating :condition of the air craft engine it-or supercharger 115, up to acertain critical speed, and thereafter tomaintain.

constant this critical speed. 7

As will become :apparentfrom the following description, quarter-phasemotor 3211s controlled by an electronic amplifier '28 which receives a controlling :signal from pressure .unit 21. Pressure unit 2-1 comprises a, sealed casing 40 which isconnected by'meansot aconduit-fll to conduit :23 ii compressor discharge or carburetorinlet pressure is to be regulated. If some other pressure .is to :be regulated, it will be obvious thatgconduit ll will be. connected to .some part of the superchargercircuit or "the :air craft i0.

-h llounted within sealed box '40 .is :a pressure re- 'sponsive means 42 which has been illustrated as a'flexible bellows. 'The' exterior of bellows 4 42 is subjected to the pressure within sealedbox 40 while the interior of bellows 42 is evacuated so that movement of bellows 42 will be in response to absolute carburetor inlet or comrl pressor discharge pressure. Withthis arrangement only a single bellows is required to regulate apredetermined absolute pressure appurtenant ,to an operating condition of supercharger lli.

1 1 i The movement or evacuated bellows 42 is op ,posed by tension spring 43. The tension of qspring may be suitably adjusted by adjust iable screw 44. Also mounted within sealed box or casing 40 is a potentiometer comprising a v utmovable arm 45 which is connected to bellows '42 so as-to be moved'th'ereby in response to expansion and contraction of bellows 42. The P ftentiometer mounted within sealed box 40 also comprises a, resistance 46 across which one end go of arm 45 is adapted to move and continuously :engage therewith. The terminals of resistance 46 are connected to the terminals of a resistance 41 which forms part of the potentiometer jcomprising manual pressure setting means 26.,

An arm 48 .similar to arm 45 completes the'potentiometer 0! manual pressure setting means 26. Suitable calibrating resistances 49 are provided in the electrical connections between the terminals of resistance 41 fllidflfi. Arms 45 and 48 are electrically interconnectedthrough the primary winding 50 oi a'flrst input transformer St. The manual pressure setting means 26 which is preferably mounted in the cabin 3| of the air craft is adjusted by the pilot or operator to main- 8 tain a predetermined pressure which through .means tobe described hereinafter causes the arm 45 of control box 21 to assume a corresponding position thereby to maintain a con-; stant pressure in sealed box 407until the critical altitude of the air craft is reached. Whenever a change in the pressure being regulated. occurs, arm -will assume a position diflerent from that of varm 48. Also arms 45 and 48,;will have difdiflers from the actual pressure in sealed box 40. i The power for energizing the potentiometer circuit comprising the potentiometers in manual pressure setting'means 26 and pressure unit nected to any suitable source 01' alternating current generally indicated at 52. As a general .rule,

a the source of alternating current on modern aircraft is 400 cycle altemating current and our 5 invention is adapted to be supplied irom a source of such alternatingcurrent. This source of alternating current illustrated schematically at 52 is connected across the terminals of resist-' ances 48 and 41 of the associated potentiometers so through a suitable manual switch 53 and a protective fuse '54.

- potentiometer circuit, no alternating current voltage will appear across the primary winding 50 or amplifier input transformer 5| unless thearms 45 and 48 ot the potentiometers including resistances 46 and 41 respectively are not positioned identically with respect to these resist- I degrees out of phase with respect to the supply potential. 52, thereby controlling amp1ifler-28 i which is polarity responsive.

Since, as will become apparent from the 7 1 ing description, a directcurrent is required for 21 isobtained from control box "which is con-.

with this arrangement oi the I .ances. The voltage across primary winding 50 of input transformer 5| will be either in phase or followcertain Purposes in connection with our regulat-' ing means, control box .25 includesa biphase rectifier generally indicated at 59 A suitable rectifier input transformer 55 is provided which has a primary winding 51 connected across the source of alternating potential 52. provided with two secondary windings .58 and 59 respectively; Secondary winding 58 is connected to energize an indicating means Gilv whenever switch 53 is closed. Winding 59, on the other hand, has its end terminals respectively connected to the anodes of a pair I valves 6|, which are arranged in the usual manner in the biphase; rectifier 55. The cathodes of valve 6| are connected'through a resistance 92 to a terminal 63 which forms the positive terminal of the output of rectifier -5, The negative terminal 64 of biphase rectifier 95 is connected,

to the midpoint of secondary winding 59. A suitable capacitor 65 connected between terminals 63 and 64, together with resistor 62, provides a Transformer 56 is of electric discharge 7 suitable filter for reducing th alternating current ripple across the direct current output.v

The motor 32 of waste gate drive 29 is an alternating current motor so as to be free, of the (hillculties often encountered with th commutators of direct current motors in high flying aircraft and furthermore is constructed so as not to require slip rings. The quarter phase windings are age appearing across the primary windings of the amplifier input transformers. Winding 61 will be energized with an alternating potential which may change in phase by 180 degrees depending upon the polarity of .the signal appearing across winding 50 of transformer 5|.

currents energizing windings 66 and 61 are displaced by substantially 90 degrees. For one direction of rotation the potential across winding 61 will lead the potential across winding 96 by substantially 90 degrees, and for the other direction of rotation will lag by substantially 90 degrees.

winding 83 of sistor 89 across which the'transient stabilizing voltage to be described hereinafter is impressed.

A single plate current limiting resistor 81 is con-- nected to the cathodes an is common to both of the plate and both of the grid circuits of twin electric discharge'valve 71; i v

The plate circuits oi'twin electric discharge valve'll are energized from an alternating curhalf-wave powe'rto each of the resistors 94 in the anode-circuits thereof. A pair discharge valves "H and 12. An alternating current potential in phase with the main power supply is also impressed on the grid-to-cathode discharge valves connecting the portion between terminals 92 and 93 01' the secondary winding or transformers in series with the grid-to-cathode circuits of electric discharge valves "H and 12 Each of these :grid-to-cathode circuits is also provided with a current limiting resistor 96. The

load connectedto'electric discharge valves 12, so as to neutralize some of the inductance thereby facilitating the initiation of 'current' flow a suitablescreen grid dropping resistor I02 t0 the common terminal of saturating windings 91 and 99.

Electric discharge valves wequal anode currents inthe II and 12 also carry same manner as the H and voltages across charge valve 12 drive motor 32 in response currents flowing in the twin triode 11 when the the primary windings of transformers and 84 respectively are zero. When an alternating current voltage in phase with the power supply is impressed across secondary wind lugs 82 of input transformer 5|, an unbalance occurs in the currents flowing through discharge valves H and 12 for example, electric discharge valve 1I may carry more current while electric discharge valve 12 may carry less. "If, however, the input voltage is 180 degrees out of phase with the plate voltage obtained from transformer 88, the unbalance will be reversed and electric diswill now carry more current than electric discharge valve 1|. v I 1 Saturable reactors 98 and 99 are each provided with altematingcurrent windings I03, I04, I05 and I08 respectively. These windings are arranged in the form of a bridge, two corners or which are connected across terminals and 89 of the alternating current source of power52. The opposite corners of the bridge are connected across phase winding 61 of wastegate driving motor 32. Under normal operating conditions when balanced currents fiow in electric discharge valves 1I and 12, relatively small balanced currents fiow in the. saturating of saturable reactors 98 and I00 respectively. It is desired, in order to save'power, to maintain the direct current flowing in the saturating windings as low as possible which is controlled by properly adjusting the magnitude of resistor 81 connected in the/plate circuit of twin triode 11. As longas balanced currents flow in-the amplifier, no current will flow in phase winding 61 of motor 32. Whenever the currents in amplifier 28 windings 91 and 99' except a transient voltageproduced when waste position which voltage is gate I0 is changing responsive to rat of change of waste gate position; With this arrangement the stabilizing means operates without any droop (recalibration of the regulating means with'change in position of waste gate I9) inthe pressure regulating means and the transient voltage drops across resistors 86 control amplifier 28 so as to eliminate any hunting in the regulator for maintaining constant the compressor discharge pressure.

As was mentioned a ve, after the aircraft attains the critical altitude which may be in the neighborhood of 25,000 feet, the speed of the supercharger I5 has increased to a-value above which it is not feasible to operate it for any long periods of time, and consequently it is desirable to provide means'for preventing this speed from exceeding the so-called critical speed. At altitudes above that corresponding to the critical speed of the supercharger, therefore, we provide regulating means to hold the speed of the supercharger constant. In order to obtain a put of high the power supply voltage, becomes saturated'more voltage, in phase with one of the reactors 91 than the other and an alternating voltage eitherin phase or 180 degrees out ofphase with respect to the plate supply voltage of two stage amplifier 28 is impressed across phase winding '61 of motor 32. Dependingupon the polarity: of this. voltage with reference to the voltage of source 52, motor 32 will rotate in one direction or the other to open or close waste gate I9. "By means of the saturable, reactors 98 and I00,-a relatively high power output can'be obtained to to a small input voltage.

To stabilize the operation of the regulating means embodying our invention we provide an anti-hunting means which is responsive directly to rate of change of waste ate position. 1 Tothis end we provide a potentiometer I01 including a resistor I08 the terminals of which are connected to the direct current supply terminals 83 and 04' of biphase rectifier 55. The movable arm I08 01' the stabilizing potentiometer is mounted on shaft 33, so as to be controlled by the movement of waste gate I9. The output terminals of stabilizing potentiometer I01are connected across resistors 86 of the grid circuits of twin triode 11. These resistors are connected in series with each other so that a potential :will

. a single control electrode, since we operate elecappear across each resistor independence upon I the current caused to flow therethrough -by',vir-

tue of the output potential of stabilizing p0tenpotentiometer I01 so that valve pears across 2 represents the characteristic, of high pass filter v III by illustrating quantity proportional to the speed of the supercharger, we have provided an alternating current or tachometer generator 30 which may be driven directly from the supercharger I5 as indicated in the drawing. The output of this generator is connected through a high pass filter III comprising a plurality of capacitors II2 and II3 and a plurality of inductances Ill and-H5. The out-1 a rectifierIIIi across aresistance load II1. A suitable smoothing capacitor II8 is. provided so that a fairly-uniform direct current potential. appears across the terminals sistor II1, I20 being the negative terminal.

and consequently at low speedsof alternating current generator 30, substantially no voltage apresistance 1. 'The curve A of Fig.

the voltage appearing across resistor II1 as the consequently the speed of tachometer 30 increases. Itwill be observed that at the critical altitude the output of filter III increases very rapidly whereas below the critical altitude.

this output is substantially negligible.

In order to utilize the voltage across resistor M1 to prevent supercharger I5 from exceeding a predetermined maximum speed, we provide an electric discharge valve I21 which may be any form of electric discharge valve well known to those skilled in the art. We have lustrate electric discharge valve I2I as a twin triode type of valve with anodes I22, cathodes I23 and control'electrodes of grids I24. Electric discharge valve I2l might equally well be a valve having but a single cathode, a single anode and tric discharge valve I2I with the anodes in parallel with one another as are also the control" electrodes so as to carry-a larger amount of current. The plate. or anode-cathode circuit of electric discharge valve I2t is connected through the primary winding of amplifier input transformer 84 68 and 89 of alternating potential source 52. The grid-to-cathode circuit of electric discharge I2I, on the other hand, is completed through current limiting'resistor I26, resistor I I1 and resistor I25. Resistor I25 is abiasing resistor and is connected across the terminals 63 pass filter III is connected through I H8 and I20 or re- II9 being the positive terminal and High pass filter I II has a characteristic so that at low frequencies speed of the supercharger and generator chosen to iland a resistor I25 to the terminals plifler input transi'ormei 51 of half-wave power which will bear a predetermined phase relationship to the alternating current potentialof source 52, the phase relationship being' either in phase,

or 180 degrees out-of-phase, depending upon the particular connections of winding 61 of waste gate motor 32. In any event the phase relationship of the voltage impressed on primary winding 85 of transformer 84 will be such as to cause waste gate motor phase winding 81 to be energized with a polarity to cause opening of waste gate iii. In other words, whenever electric discharge valve i2| becomes conducting, motor 22 will be energized to open waste gate is. Furthermore, the ratios of transformation of input transformers 5| and 54 are such that a voltage appearing across primary winding 85 of transformer 54 will take control over a voltage appearing across primary winding 50 of transformer 5|.

It will be obvious that the follow-up mechanism or anti-hunting means used for stability operation and described in connection with the pressure regulating means above operates in exaotly the same manner on the overspeed control as it does with regard to regulating pressure.

The operation of the turbosupercharger regulator described will be fairly obvious from the detailed description included above. Assume that the aircraft is in the air and is flying at an altitude lower than the critical altitude of the supercharger, that is, at an altitude below the maximum for which the supercharger is capable of maintaining without excess speed a predetermined pressure at the discharge side of the compressor, for example, sea level pressure. Assume also that at such altitude, waste gate is is in a partially closed position as indicated in the drawing, and the supercharger is operating at a speed such that the desired pressure obtains on the discharge side of compressor II of supercharger l5. With this arrangement. potentiometer arm '45 of pressure unit 21' will be positioned in response to absolute compressor discharge pressure for operation of bellows 42. If, now, for some reason, the pressure on the discharge side of compressor il decreases, the pressure within sealed box 40 will decrease and bellows 42 will expand so that spring 43 will move regulating arm 45 compresssor il. Movement of waste gate I O to the closed position will also cause arm Hi9 of stabilizing potentiometer. I01 to move to the left as viewed in Fig. l and introduce a transient stabilizing voltage across resistors 86 so as to cause deenergization of phase winding 51 of motor 32 before waste gateifl has closed too far. By properly adjusting, the regulator, the pressure in sealed box 40. will increase rapidly at first and then slow down its before it reaches the value called for stoppi at this value with no overshooting or undershooting.

When the critical altitude is reached, that is the altitude at which maximum desired speed of supercharger i5 is obtained, the output of generator 30 and high pass filter iii is such that the voltage across resistor ill will overcome the voltage across bias resistor I25 and cause electric discharge valve III to become conducting, which causes a voltage to be impressed across primary winding 85 of amplifier input transformer 84 of such a phase position relative to the phase of alternating source 52 as to energize winding 51 of motor 32 to cause opemng of waste gate is. If the speed of supercharger I5 is reduced too far, the pressure regulating means including pressure unit 21 will again take control and maintain constant pressure up to the critical altitude.

With the invention described above it is possible to obtain close automatic and stable operation of the turbosupercharger with improved apparatus which is very simple in construction and reliable in operation. Furthermore, all connections of the fluid or mechanical nature are very short and the only connection between parts of the apparatus which are of any length whatever are electrical.

While we have shown and described a particular'embodiment of our invention, it will be apparent to those skilled in the art that our invention is not limited to the particular embodiment shown, but that changes and modifications may across resistor 46 toward the left with reference turbine wheel It with consequent increase in speed of supercharger l5. Such increase in speed be made without departing from the spirit and scope of our invention, and we aim in the appended claims to cover all such changes and modifications.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. In combination, a turbosupercharger actuated by exhaust gases, valve means for regulating the flow of exhaust gases to the turbine. a motor for controlling said valve means, and means responsive to a predetermined pressure appurtenant to an operating condition of said supercharger for positioning said valve means to maintain said predetermined pressure at a substantially constant value over a predetermined range of operation comprising a plurality of units interconnected solely by electrical leads including a manual pressure setting means, a pressure unit mounted adjacent said pressure 'to be regulated, and an amplifier responsive to changes in the pressure to be regulated for amplifying said pressure changes arranged to control phase winding of said motor from said source or.

- alternating current, an electronic amplifier including a saturable reactor for energizinganwill tend to increase the discharge pressure of other phase winding of said motor with an alterfier to cause said motor to position said waste gate so as to maintain said pressure at a substantially constant value over a predetermined range of operation.

3. In combination, a turbosupercharger actuated by exhaust gases, a waste gate for regulating the fiow of exhaust gases to the turbine, a polyphase alternating current motor for positioning said waste gate, a source of alternating current, means for continuously,.energizing one phase winding of said motor from said source of alternating current, an electronic amplifier for energizing another phase winding of said motor withan alternating current which either leads or lags said alternating current of said source to cause rotation of said motor either in one direction or the other, means responsive to a predetermined pressure appurtenant to an operating condition of said supercharger for controlling said amplifier-to cause said motor to position said waste gate and maintain said pressure at a substantially constant value over a predetermined'range of operation, and speed responsive means driven by said supercharger for controlling said amplifier and consequently said motorfor positioning said waste gate'at speeds of said supercharger above the highest speed within said range of operation.

4. In combination, a turbosupercharger actuated by exhaust gases, a waste gate for regulating the fiow of exhaust gases to the turbine, a polyphase alternating current motor for positioning said waste gate, a. source of alternating current, means for continuously energizing one phase-winding or said motor from said source of alternating current, an electronic amplifier for energizing another phase winding of said motor iwith an alternating current-which either leads-or lagssaid alternating current of said source to cause rotation of said motor either in one direction or the other, means responsive to 6. In combination, a tur osupercharger actuated by exhaust gases, valve means for regulating the flow of exhaust gases to the turbine, an electric motor for positioning said valve means, means including an electronic amplifier responsive to a predetermined pressure appurtenant to an opcrating condition or said supercharger for energizing said motor to position said valve means to maintain said predetermined pressure at a substantially constant value over a predetermined range of operation, means for controlling said amplifier in response to supercharger speed outside said range of operation to prevent said supercharger from exceeding a predetermined speed comprising means responsive to the speed of said supercharger, and a high pass filte connected between said last mentioned means and said amplifier for preventing said last mentioned means from becoming efiective until said predetermined speed has been attained.

'7. In combination, a, turbosuperchargeractuated by exhaust gases, a waste gate for regulating the flow of exhaust-gases to the turbine, an electric motor for positioning said waste gate, means for controlling the energization of said motor to position said waste gate and maintain constant a predetermined pressure appurtenant to an operating condition of said supercharger including an electronic amplifier responsive to changes in said predetermined pressure, means responsive to speeds above a, predetermined maximum speed of said supercharger for taking over control of said amplifier and preventing said maximum speed from being exceeded, and

stabilizing means responsive to rate of change of waste gateposition to insure that said waste gate a predetermined pressure appurtenant to an op- I crating condition of said supercharger for .controlling said amplifier to cause said motor to position said waste gate and maintain said pressure at a substantially constant value over a predetermined range of operation, and speed re sponsive'means including a high pass'filter and I an alternating current generator driven by said supercharger for controlling said amplifier and consequently said motor for positioning said waste gate at speeds of said supercharger above the highest speed within said range of operation.

5. In combination, a turbosupercharger actuated by exhaust gases, a waste gate for regulating the flow or exhaust gases to the'turbine. an electric motor for positioning said waste gate,

, means to: controlling the energization of said motorto position said waste gate, and maintain constant a predetermined pressure appurtenant to an operating condition or said supercharger including an electronic amplifier responsive to changes in said predetermined pressure for amplifying said changes in said predetermined pressure for controlling said motor, and means responsive to speeds above a predetermined maximum speed of said supercharger for taking over control of said amplifier and preventing said maximum speed from being exceeded.

is positioned without over or under shooting the correct position.

8. In combination, a turbosupercharger actuated by exhaust gases, a waste gate for regulating the fiow of exhaust gases to the turbine, a polyphase alternating current motor for positioning said waste gate, a source of alternating current,

means for continuously energizing one phase winding of said motor from said source of alternating current, an electronic amplifier for energizing another phase winding of said'motor with arr-alternating current which either leads or lags said alternating current of said source to cause rotation of said motor either in one direction or the other, means responsive to a predetermined pressure appurtenant to an operating condition of said supercharger for controlling said amplifier to cause said motor to position said waste gate so as to maintain said pressure at a substantially constant value over a predetermined range of opera-tion, and stabilizing nieans responsive to rate of change or waste gate position to insure that said waste gate is positioned without over or under shooting the correct position.

" MARTIN A. EDWARDS.

V HUGH M. OGLE.

REFERENCES crrnn The following references are of record in the file ofthis'patent:

UNITED STATES PATENTS Disclaimer 2,425,607.Martin A. Edwards, Scotia, and Hugh M. Ogle, Schenectady, N. Y. CONTROL SYSTEM FOR AIRCRAFT TURBOSUPERCHARGERS. Patent dated Aug. 12, 1947. Disclaimer filed Dec. 8, 1948, by the assignee, General Electric Company. Hereby enters this disclaimer to claims 1, 2, 3, and 5-of said patent.

[Oflicial Gazette January 11, 1949.] 

